On Tue, Mar 29, 2016 at 08:22:00AM -0400, Xiao Ni wrote: > Hi all > > I encountered one NULL pointer dereference problem. > > The environment： > latest linux-stable and mdadm codes > aarch64 platform > the md device is created with loop devices > > It's a test case to check date integrity. I added the test script as the attachment. Could you please try this patch: >From b86d9e1724184c79ad1ea63901aec802492b861c Mon Sep 17 00:00:00 2001 Message-Id: <b86d9e1724184c79ad1ea63901aec802492b861c.1459285706.git.shli@xxxxxx> From: Shaohua Li <shli@xxxxxx> Date: Tue, 29 Mar 2016 14:00:19 -0700 Subject: [PATCH] MD: add rdev reference for super write md_super_write() and corresponding md_super_wait() generally are called with reconfig_mutex locked, which prevents disk disappears. There is one case this rule is broken. write_sb_page of bitmap.c doesn't hold the mutex. next_active_rdev does increase rdev reference, but it decreases the reference too early (eg, before IO finish). disk can disappear at the window. We unconditionally increase rdev reference in md_super_write() to avoid the race. Reported-by: Xiao Ni <xni@xxxxxxxxxx> Cc: Neil Brown <neilb@xxxxxxx> Signed-off-by: Shaohua Li <shli@xxxxxx> --- drivers/md/md.c | 3 +++ 1 file changed, 3 insertions(+) diff --git a/drivers/md/md.c b/drivers/md/md.c index c068f17..bcfde333 100644 --- a/drivers/md/md.c +++ b/drivers/md/md.c @@ -718,6 +718,7 @@ static void super_written(struct bio *bio) if (atomic_dec_and_test(&mddev->pending_writes)) wake_up(&mddev->sb_wait); + rdev_dec_pending(rdev, mddev); bio_put(bio); } @@ -732,6 +733,8 @@ void md_super_write(struct mddev *mddev, struct md_rdev *rdev, */ struct bio *bio = bio_alloc_mddev(GFP_NOIO, 1, mddev); + atomic_inc(&rdev->nr_pending); + bio->bi_bdev = rdev->meta_bdev ? rdev->meta_bdev : rdev->bdev; bio->bi_iter.bi_sector = sector; bio_add_page(bio, page, size, 0); -- 2.8.0.rc2 -- To unsubscribe from this list: send the line "unsubscribe linux-raid" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
